This invention relates to differential servo-motors and more particularly to the type of servo-motors used to operate the hydraulic brake systems of motor vehicles.
Various differential servo-motors have been proposed heretofore for use on automotive vehicle brake systems to enable the substantial manual effort for braking to come into play after actual braking begins as disclosed and described specifically in prior U.S. Pat. No. 3,013,533 in recognition of advantages of smaller initial manual force to initiate braking but of a relatively uniform relationship of manual force and power throughout the entire braking range.
In such servo-motors, the foregoing object and others are attained through an additional provision of a reaction element in the form of a large ring made of resilient, flexible material such as rubber in addition to the ordinary associating parts with an aim that powered effort supplied by the servo-motor in the early stage of braking will sufficiently overcome the unavoidable resistance of return springs and the friction of certain movable parts in the servo-motor, master cylinder and in the actuators and at the brake shoes of the foundation brake unit.